Perhaps the place to start with is in doing some serious reading?
The internet is filled with folks who will give you resourceful answers as to what "they" think. Ater wading thru all the replies the waters could very well be so muddy that your head is swimming also.
Great Reading for the beginer are:
1. SPG Reloading Primer, by Venturino and Garbe.
2. Black Powder Cartridge Silhouette Handbook, by Croft Barker.
3. Black Powder, Pig Lead & Steel Silhouettes, by Paul Matthews.
4. Shooting Buffalo Rifles of the Old West, by Venturino.
For about $100.00 the four publications will reveal more than one can evaluate in one reading of each. They will remain as constant reference works for the remainder of your life. Mostly they will reveal what you personally will determine as to what you don't want!
Trying to find a "bargain" purchase in a black powder silhouette rifle can lead to some real reduced quality items. You can bet if the various firearms manufacturers are NOT mentioned in the above publications, there is good reason. Ditto with accessories (sights) and loading components.
Monthly, bi-monthly and quarterly publications are also great investments. Black Powder Cartridge News, Single Shot Exchange, Shoot Magazine, etc.
Finding where Black Powder Cartridge Rifle Shoots are held will also add to your knowledge. Attend a shoot and look at the equipment being used. Ask questions and be prepared to listen to the multitude of answers and opinions. Ask more questions. Surely someone will offer to let you pull the trigger on a few rounds and knock down some steel. You'll be hooked............
Welcome to the club!